One of Mexico City's most significant monuments – and one that few tourists have heard of, let alone seen – is nearing the final stages of a 17-year-long restoration effort, a year after being listed on the World Monuments Fund's biennial Watch List. The Ruta de la Amistad, or Road of Friendship, is a collection of 22 gargantuan sculptures commissioned from internationally-known artists from five continents for the 1968 Olympics.

Creation of the Ruta de la Amistad, the world's largest sculpture corridor, was a remarkable undertaking. The abstract concrete-and-steel sculptures, some upwards of 80 feet high, stretched over 10 miles along a road that linked distant Olympic venues in the southern reaches of the huge capital. Nineteen were built along the roadside, and another three were built nearby at Olympic sites. The area had nothing to draw a tourist, except those attending the Olympics that year. As the city's inexorable growth surrounded and obscured the sculptures, the road became a major highway, today's Periferico Sur. The sculptures stood neglected and all but forgotten.

Space-age daydream

Though the former Olympics locations are now smack in the middle of a dense urban zone, it's still the rare tourist who ventures to the area, which lies 30 minutes to as much as two hours (depending on traffic) from the historic heart of Mexico City.

Rarer still are visitors who have seen the sculptures, although we have Raquel Welch to thank for keeping their images alive in some small measure. The reigning sex symbol's 1970 dance video, performed in a sort of space-age version of her fur bikini in "One Million Years B.C.," was set to great effect against the intriguingly bizarre shapes and colors of the Amistad sculptures, which dwarf the dancers.

The sculptures express a 1960s view of modernism, such as Mexican sculptor Ángela Gurría's "Signs," a pair of inverted apostrophes piercing the sky; Czech sculptor Miloslav Chlupac's "The Three Graces," resembling pink and purple bamboo shoots; "Spheres," stark white Pac Man shapes by Japanese sculptor Kioshi Takahashi; and the Italian sculptor Costantino Nivola's set of angular white blocks striped in red and green, called "Man of Peace."

Spanish sculptor José María Subirachs' "Mexico" consists of black and white geometric shapes that recall Aztec archaeological sites. Despite their size, the only Amistad sculpture with a functional interior is Uruguayan sculptor Gonzalo Fonseca's "Tower of the Winds," which looks a bit like a circular adobe fortress from the outside. Its light-filled interior hosts rotating art installations.

Turning point in Mexico's history

The nonprofit World Monuments Fund identifies threatened historic architecture and cultural heritage sites and uniquely significant monuments. Then, through a combination of direct funding, training, technical support and partnership with local groups, governmental agencies and other funding sources, it helps to preserve them. Over the past 47 years, it has had a hand in protecting some of the world's most-visited sites, including Cambodia's Angkor Wat, Chile's Easter Island, the Egyptian Pyramids, New York's Ellis Island and Taos Pueblo in Mesa Verde National Park. But just as many of their projects take them to villages, churches and other important repositories of cultural heritage that most tourists might never hear of unless they are familiar with the WMF's work.

The Amistad sculptures fit into the latter category, though that should change after the restoration project is complete. They don't have the drawing power of the ancient city of Teotihuacan or the Palacio de Bellas Artes in Mexico City's historic center – both of which WMF has worked on – but the Ruta de la Amistad was part of a major shift in Mexico's focus and identity in the 1960s. The sculptures were commissioned to celebrate world harmony during a time of expectation and optimism, when the country was undergoing a transformation from Third World to developing nation and becoming more involved in international trade and cultural exchange.

The final stretch

The Patronato Ruta de la Amistad, a local conservation organization, began working to restore and preserve the sculptures in 1994, and had completed work on 18 when the WMF stepped in last year. Construction of a new elevated second level on the Periferico Sur was beginning, and according to Norma Baldacci, WMF's Director of Programs for Latin America, "The sculptures were not legally projected as landmarks, and engineers' maps did not include them. So they planned the second-story supports without consideration of existing sculptures."

The threat of demolition forced relocation of almost all of the sculptures. Most are grouped in two huge cloverleaf intersections that have been transformed into parks, making the restored sculptures accessible again. As a bonus, the Lava Flow Gardens – exposed lava deposits that figured into the original design of the Ruta de La Amistad – have also been excavated so that the sculptures' surroundings are truer to the original even though they have been moved.

Three sculptures that still awaited restoration and relocation have the WMF's primary focus since listing the sculptures on its 2012 Watch List:

— Untitled (Olivier Seguin, France): a meandering concrete sculpture by an artist who lived and created his first internationally acclaimed works in Mexico during the 1960s.

The WMF is also creating informational material recounting the decades-long preservation effort and has hosted public events and promotions to announce the sculpture's rehabilitation. The new venues will also host contemporary art installations that will cement be the Amistad collection's re-emergence in Mexico City's public life.

Former Chronicle travel editor Christine Delsol is the author of "Pauline Frommer's Cancún & the Yucatán" and a regular contributor to "Frommer's Mexico" and "Frommer's Cancún & the Yucatán."